Overview
This research reports the direct generation of spin-photon entanglement in the telecom C-band and its subsequent use to verify quantum nonlocality. The work utilized a single rubidium atom to emit C-band telecom photons at 1530 nm, achieving a Bell state fidelity greater than 91.4%.
Research Context
Quantum nonlocality is a fundamental aspect of quantum information science, typically manifested through entanglement distributed across quantum networks. For long-distance entanglement distribution, the information carrier, often flying photons, needs to operate within the minimum-loss telecom band of optical fiber. Previous efforts have focused on directly generating entanglement between C-band telecom photons and various stationary spins. However, verifying quantum nonlocality in such systems has remained a challenge.
Approach
The research employed a dipole transition in rubidium atoms, specifically targeting a wavelength of 1530 nm, which falls within the C-band telecom range. A cavity-assisted protocol was implemented to facilitate resonant excitation and direct emission of C-band telecom photons from a single atom. This approach aimed to generate entanglement between the atomic spin and the emitted photon.
Findings
- The wavelength of a single-atom quantum emitter was extended to the telecom C-band.
- Direct generation of spin-photon entanglement was achieved from a single atom using C-band telecom photons.
- The measured Bell state fidelity of the generated spin-photon entanglement exceeded 91.4%.
- Bell nonlocality was verified through the observation of a Bell inequality violation. The observed violation was $2.455(77) \pm 2$. This value surpassed the threshold for a Bell inequality violation, confirming quantum nonlocality.
- The fidelity of the spin-photon entanglement was sufficient to enable the verification of Bell nonlocality.
Why This Matters
The successful generation of high-fidelity, C-band spin-photon entanglement and the subsequent verification of Bell nonlocality provide a promising building block for advanced quantum technologies. This work has implications for the development of large-scale atom-based quantum networks. Such networks are envisioned to support distributed quantum metrology and long-distance quantum communication.